Building panels—specifically acoustically pervious ceiling panels—have a tendency to sag when exposed to high-humidity environments. These building panels, which are formed from a combination of starch, and other binders, organic and inorganic fiber, and optional filler, are put under added stress in high-humidity environments because the amount of water absorbed by the building panel increases and, starch as well as many polymeric binders are hydrophilic and lose strength when exposed to humidity. With enough exposure to high-humidity, the structural integrity resulting from bond between the binder and the fiber and/or filler is compromised causing the building panel to sag downward. Additionally, such building panels may exhibit staining on the exposed faces after prolonged exposure to moisture.
Previous attempts at preventing such sagging and included adding large amounts of polymeric binder to the building panel. Substituting hydrophilic binders with high strength hydrophobic binders may increase sag resistance of the panel under humid conditions, however these binders are far more expensive than the existing water sensitive binders. Thus, there exists a need for a building panel having greater resistance to sagging and/or face-staining over prolonged periods of exposure to moisture.